Leaf anatomical characteristics and differential chlorophyll loss in selected "stay- green" wlid rices (Oryza spp.)

Date

4-2003

Degree

Bachelor of Science in Biology

Major Course

Major in Cell Biology

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Nina M. Cadiz

Abstract

Variations in leaf anatomical characteristics and chlorophyll loss in selected "stay-green" wild rices (Oryza spp) were determined. Wild rites have been rich sources of genes for rice improvement and identifying one with delayed foliar senescence can help develop cultivars with increased grain yield. Evaluation of their "stay-green" characteristics revealed that after 10 days of dark incubation in distilled water, spectrophotometrically determined chlorophyll a, b and total chlorophyll were highest in O. ridleyi (1.6714, 1.4352, 3.5404 mg/g) and lowest chlorophyll b and total chlorophyll in O. officinalis 100896 x O. officinalis 10116 (0.1811, 0.4047 mg/g). However, the initial measurements of chlorophylls from fresh leaf samples showed that these pigments were highest in 0. officinalis 100896 x 0. officinalis 10116 (1.8531, 1.7309, 4.1364 mg/g). The very weak linear correlations obtained between initial and final chlorophyll a (r=0.14), b (r=0.12) and total chlorophyll (r=0.08) were not statistically significant. The level of endogenous cytokinins assayed was also highest in 0. ridleyi (1.78 ppm) and lowest in 0. officinalis 100896 x O. officinalis 10116 (0.0004 ppm). Senescence was delayed longer in rices of O. ridleyi and 0. meyeriana complex than those in O. officinalis complex. Anatomical characterization of leaves showed markedly different internal structure in l'orteresia coarctata lamina showing a continuum of prominent ribs and furrows containing two files of vascular bundles and no midrib. The presence of air cavities within the midrib of O. ridleyi was noted. Chlorenchyma was thickest in 1'. coarciaw (292.6 }cm) and thinnest in O. eichingeri (48.8pm). Distance between vascular bundles of the lamina was farthest in P. coarcww/O. minuta (150gm) and closest in 0. eichingeri (120 pm). The very weak negative correlation of vascular bundle distance to final total chlorophyll content (r = -0.11) was not statistically significant. Based from the results, 0. ridleyi showed the greatest potential as a donor in developing "stay-green" rice with delayed senescence and thus, longer leaf longevity favorable in the export of more photosynthates to developing grains.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

Thesis

Document Type

Thesis

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